Light-projecting apparatus



Aug. 4, 1925.

F. BENFORD LIGHT PROJECTING APPARATUS Filed June 29, 1922 Inveritov:Frank A. Benford,

His Attrey Patented Aug. 4:, 1925.

hilTED STATES AT @FLFEQE.

FRANK A. BENFORD, OF SCI-IENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELEC-TRIO COMPANY, A CDBPORATION OF NEW YORK.

LIGHT-PROJECTING APPARATUS.

Application filed June 29, 1922.

To all whom it may concern:

Be it known that I, FRANK A. BnNronn, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements inLight-Projecting Apparatus, of which the following is a specification.

My invention relates to projector systems in which light from suchsources as the high intensity are are carried through a condenser lensto a screen or other background. I-Ieretofore, when the light emitted bythe crater of the positive electrode and by the tip of the negativeelectrode was thrown upon a condensing lens, this lens produced not onlythe image of the crater upon the screen but also an image of thenegative electrode tip and of the flame of the are above the image ofthe crater. In this way, two spots were obtained instead of oneconnected by the image of the flame. The negative spot in some instances0btrudes upon the region of the positive spot, which is alsoobjectionable.

Among the objects of my invention are following: To provide a screenbetween the negative electrode, the flame of the arc and the condenserwhich will entirely shield the electrode while the light from thepositive electrode is unobstructed and to provide detailed construction,all of which are hereinafter more fully set forth and claimed.

Referring to the accompanying drawing,

Fig. 1 is aview in side section in elevation, showing the shield inplace; Fig. 2 is a front view in elevation of the shield; Fig. 3 is afront view in elevation of the head of the shield shown in connectionwith the radiating system.

Referring more in particular to the drawing, Fig. 1, the are 2 isindicated between the positive and the negative electrodes 3 and 4respectively of the well known type of high intensity are. At the leftis shown the condenser support frame A. Near the central portion of thesupport frame is shown the lens 5. Screwed to the frame of the lens is ahood 6 which may be made of any suitable material such as sheet iron,copper or the like. On the nose of the cone I have provided a heatresisting head or nozzle 7 which may he made of such material asaluminum bronze. An 8% composition may loe used in which the aluminumSerial No. 571,769.

is 8% per cent of the total. This head must necessarily be of highrefractory character on account of the intensity of the arc. I haveindicated the same as being of substantial thickness. This head may beprovided with radiating ribs to promote the radiation. The nozzle 7 ismade, as shown, with a heavy heel, Fig. 1, just above the electrode 4.The central section of the nozzle, as indicated in Fig. 1 is formed tofollow the outline of the flame of the are 2. This flame is intenselyhot and particularly so in the high intensity are. This heat is so greatthat there is scarcely anything that will withstand the temperature forany length of time. It is to avoid this intense field that the nozzle ismade in the particular form indicated along its central section. Theupper portion of the nozzle is so constructed as to flare to the rightand to the left, see Fig. 3, and at the same time taper off into acompartively thin rim. The object of this construction is to insure arapid dissipation of the heat imparted to the nozzle from the arc. Ialso contemplate using a head which is hollow, as indicated in Fig. 3,and in connection with which I propose using a radiating system throughwhich a fluid of any suitable character may be caused to circulate;water, for example, may

be used to advantage. This head 7 may be secured to the hood 6 bysuitable springs 10, as indicated in Fig. 2. On the other hand, the hooditself is secured to the frame A by means of the screws 13 which arereceived by the slots 12 shown around the base of the cone. It will beunderstood that the hood 6 may be of any suitable shape, for example, itmay be conical or in the shape of a pyramid. With this arrangement, thelight from the positive electrode passes through the opening 11 in thenozzle and hood in the form of a tapering beam which strikes the lens 5.The apex of this beam is the positive crater and the sides aredetermined by the aperture 11. The hood 6 operates to cut off any lightfrom the lens which originates outside of the crater, as, for example,from the negative electrode 4 or from the flame of the are beyond theimmediate region of the positive crater. As indicated in Fig. 3 inconnection with the hollow form of head 7, I provide a radiator 8 whichis connected with the head 7 by way of the conducting pipes 9 and 10back into the head 7.

The hot fluid of course rising through the pipe 9, reaches the radiator8, where it is cooled and passes down through the pipe 10' ViTith theusev of such an arrangement, I obtain a. clear cut illumination upon thescreen, devoid of any of the objections above indicated.

While I have described my invention in connection with a form ofapparatus shown in the drawing it will be understood thatI donot limitmyself to this specific form of apparatus inasmuch as variations of myinvention may readily suggestthemselves to those familiar with this artthat do not depart from the spirit thereof or from the scope of theclaims contained herein.

hat I claim, as new and desire to secure by Letters Patent of the UnitedStates, is:

- 1. In a projector, a lens, an arc lamp having a pair of electrodes thepositive crater oi which is located in front of the lens at a pointalong theoptical axis of the projector whereby a tapering beam of lightoriginating at said crater and having an axis which coincides: with thesaid optical axisv is, intercepted bythe lens, a. hood about said beamfor cutting off light from the lens originating outside of the saidcrater, said hood provided with an opening in juxtaposition to thecrater through which opening said beam passes, and a nozzle about saidopening for determining the outline of the arc flame. i

2. In a projector, a lens, an are having a pair of electrodes thepositive crater of which is located in front of the lens at a pointalong the optical axis of the projector whereby a tapering beam of lightoriginating at said crater and having an axis which coincides with thesaid optical axis is intercepted by the lens, a hood about said beam forcutting off light from the lens originating outside of the said crater,said hood provided with an opening in juxtaposition to the craterthrough which said beam passes, and a nozzle about said opening fordetermining the outline of the arc flame, said nozzle provided with aheavy heel on one side of the arc and; tapered therefrom to form acomparatively thin rim whereby the heat imparted by the arc may berapidly dissipated.

3. In a projector, a lens, an are having a pair of electrodes thepositive crater of which is located in front of the lens at :1

ing for determining the outline of the arc flame, said nozzle formed ofa good heat conducting. material with a cavity provided with acirculating;- fluid for dissipating the heat imparted to the nozzle bythe arc.

at. In a projector, a lens, an are having a pair of electrodes thepositive crater of which is located in front of the lens at a pointalong the optical axis. of the projector whereby a tapering beam oflight originating at said crater and having an axis which coincides withthe said optical axisis intercepted by the lens, a hood about said beamfor cutting oli light from the lens originating outside of the saidcrater, said hood provided with an opening in juxtaposition to thecrater through which said beam passes, and a nozzle about said openingfor determining the outline of the arc flame, said nozzle formed ofaluminum bronze. i i

In; witness whereof I have hereunto set my hand this 28th day of June,1922.

FRANK A. BENFORD.

